Download Interleukin-6 release from human abdominal adipose cells is

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Hyperthyroidism wikipedia , lookup

Hypothyroidism wikipedia , lookup

Graves' disease wikipedia , lookup

Transcript
Am J Physiol Endocrinol Metab 290: E1140 –E1144, 2006;
doi:10.1152/ajpendo.00516.2005.
Interleukin-6 release from human abdominal adipose cells is regulated
by thyroid-stimulating hormone: effect of adipocyte differentiation
and anatomic depot
T. T. Antunes,1 A. Gagnon,1 B. Chen,2 F. Pacini,3 T. J. Smith,2 and A. Sorisky1
1
Department of Medicine and Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa Health
Research Institute, Ottawa, Canada; 2Division of Molecular Medicine, Department of Medicine, Harbor-University
of California Los Angeles Medical Center and the David Geffen School of Medicine at the University of California
Los Angeles, Torrance, California; 3Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy
Submitted 25 October 2005; accepted in final form 5 January 2006
(CVD) in longitudinal prospective studies (6, 30, 32, 38). It
may act directly at the vessel wall or indirectly by stimulating
hepatic production of C-reactive protein (CRP), a novel CVD
risk marker (25, 31). Because adipose tissue makes a significant contribution to the level of IL-6 in the circulation (27), it
is important to identify the factors that influence IL-6 secretion
from this tissue. We have demonstrated that TSH stimulates
IL-6 release from 3T3-L1, 3T3-F442A, and human differentiated adipocytes in culture (5).
Elevated TSH secretion in subclinical hypothyroidism (mild
thyroid gland failure) serves to maintain normal thyroid hormone levels, and, interestingly, this thyroid disorder has been
associated with CVD (8, 13, 15, 19, 22, 33, 39). Traditional
CVD risk factors do not clearly account for the association, but
recently CRP was found to be higher in patients with subclinical hypothyroidism (7, 36). This clinical finding is consistent
with our cellular studies linking TSH to IL-6 production in
adipocytes, given that IL-6 is a major regulator of CRP production (25).
To broaden our knowledge of TSH action on IL-6 release
from human adipose cells, we have investigated the effects of
stage of adipocyte differentiation and anatomical site of adipose tissue depot on this process. Stromal preadipocytes and
differentiated adipocytes derived from paired samples of abdominal subcutaneous and omental fat depots were studied. In
addition, serum levels of IL-6 were measured in thyroidectomized patients treated with recombinant human (rh) TSH as a
measure of extrathyroidal action of TSH in vivo.
preadipocyte; adipose tissue; thyroid; adipokine; inflammation
MATERIALS AND METHODS
thyroid-stimulating hormone (TSH)
does not exclusively target the thyroid gland but also acts on a
variety of other cells, including preadipocytes and adipocytes
(10, 11). Adipose tissue, in addition to its crucial role in
lipogenesis and lipolysis, also influences metabolic and vascular health through its secretion of cytokines (adipokines; see
Ref. 21). TSH-mediated preadipocyte and/or adipocyte responses include proliferation, differentiation, survival, lipolysis, and leptin secretion (3, 16, 20, 26, 34).
Interleukin-6 (IL-6) is a proinflammatory adipokine that is
associated with an elevated risk of cardiovascular disease
Isolation, culture, and differentiation of human stromal preadipocytes. Paired samples of abdominal subcutaneous and omental adipose
tissues (⬃1–2 g wet wt) were obtained from five patients (4 female,
1 male) undergoing elective abdominal surgery (3 total abdominal
hysterectomies, 1 bowel resection, and 1 gastrojejunostomy) with the
approval of the Ottawa Hospital Research Ethics Committee (no.
1995023-01H). Their age was 51.4 (SD 7.3) yr, and body mass index
was 26.6 (SD 3.7) kg/m2. The hospital record noted they were not
acutely ill, were weight stable, and did not have diabetes, renal, or
infectious disease. Two had well-controlled hypertension, one of
whom was also known to have stable coronary artery disease, and
were treated with candesartan, hydrochlorothiazide, losartan, verapamil, and simvastatin. Of the four women, two were postmeno-
Address for reprint requests and other correspondence: A. Sorisky, Ottawa
Health Research Institute, 725 Parkdale Ave., Ottawa, ON, Canada K1Y 4E9
(e-mail: [email protected]).
The costs of publication of this article were defrayed in part by the payment
of page charges. The article must therefore be hereby marked “advertisement”
in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
IT IS NOW RECOGNIZED THAT
E1140
0193-1849/06 $8.00 Copyright © 2006 the American Physiological Society
http://www.ajpendo.org
Downloaded from http://ajpendo.physiology.org/ by 10.220.33.1 on May 10, 2017
Antunes, T. T., A. Gagnon, B. Chen, F. Pacini, T. J. Smith, and
A. Sorisky. Interleukin-6 release from human abdominal adipose cells
is regulated by thyroid-stimulating hormone: effect of adipocyte
differentiation and anatomic depot. Am J Physiol Endocrinol Metab
290: E1140 –E1144, 2006; doi:10.1152/ajpendo.00516.2005.—Adipose cells are extrathyroidal targets of thyroid-stimulating hormone
(TSH). TSH stimulates interleukin-6 (IL-6) release from adipocytes.
We examined TSH responsiveness as a function of stage of differentiation or adipose tissue depot in cultured adipose cells and determined the effect of TSH on extrathyroidal IL-6 production in vivo.
Stromal preadipocytes, isolated from human abdominal subcutaneous
or omental adipose tissue, and their differentiated counterparts were
studied. IL-6 protein concentration in the medium was measured after
TSH stimulation. Basal IL-6 release was greater for preadipocytes
than differentiated adipocytes, whether derived from subcutaneous or
omental fat depots. A depot-dependent effect (omental ⬎ subcutaneous) on basal IL-6 release was observed for preadipocytes (1.6-fold,
P ⬍ 0.05); a similar trend for differentiated adipocytes was not
significant (6.2-fold, P ⬎ 0.05). IL-6 responsiveness to TSH was
observed upon differentiation, but only for subcutaneous adipocytes
(1.9-fold over basal, P ⬍ 0.001). To determine if TSH could stimulate
IL-6 release from extrathyroidal tissues in vivo, we measured serum
IL-6 levels from five thyroidectomized patients who received recombinant human (rh) TSH and found that levels increased by threefold
on days 3 and 4 (P ⬍ 0.05) after its administration. Our data
demonstrate that stage of differentiation and fat depot origin affect
basal and TSH-stimulated IL-6 release from adipose cells in
culture. Furthermore, rhTSH elevates serum IL-6 response in
thyroidectomized patients, indicating an extrathyroidal site of TSH
action.
TSH STIMULATES IL-6 RELEASE FROM ADIPOSE CELLS
and TSH were measured in thawed samples by an ELISA kit (Alpco
Diagnostics, Windham, NH) and by chemiluminescence (Elecsys
2010; Roche Diagnostics, Indianapolis. IN), respectively.
Statistical analysis. Data were analyzed by ANOVA and the
Newman-Keul’s test for multiple comparisons (P ⬍ 0.05 considered
significant).
RESULTS
Basal IL-6 release was measured in medium obtained after
4 h of incubation with the cell cultures. To examine the effect
of stage of differentiation and adipose tissue depot, we compared basal IL-6 secretion from stromal preadipocytes and
differentiated adipocytes derived from either the abdominal
subcutaneous or omental adipose tissue depots. As shown in
Fig. 1, mean basal IL-6 release was 30-fold (P ⬍ 0.01) and
8-fold (P ⬍ 0.001) higher from stromal preadipocytes vs.
differentiated adipocytes from the subcutaneous and omental
depots, respectively. In the case of stromal preadipocytes,
those from the omental depot released 1.6-fold more IL-6 (P ⬍
0.05). Omental differentiated adipocytes also released more
IL-6 than subcutaneous differentiated adipocytes, but this difference did not reach significance.
The response to treatment with 1 ␮mol/l TSH was assessed
by comparing each condition with its respective control, given
the very different basal IL-6 values (Fig. 1). TSH increased
IL-6 release by differentiated subcutaneous adipocytes by 90%
over basal (Fig. 2). This approximately twofold stimulation is
consistent with our previous study on subcutaneous differentiated adipocytes (5). The responses of the preadipocytes from
either depot, as well as the differentiated omental adipocytes,
were ⬃35– 40% and did not reach significance. The omental
preadipocytes did not become more TSH responsive upon
differentiation, in contrast to the differentiation of subcutaneous preadipocytes.
To address the question of whether TSH could act on
extrathyroidal tissue targets in vivo and elicit an increase in
serum levels of IL-6, we obtained serial blood samples for
measurement of TSH and IL-6 from five male patients who had
previously undergone surgical thyroidectomy followed by radioactive iodine ablation of any residual thyroid tissue. They
received rhTSH injections in preparation for routine radioactive iodine body scans for thyroid cancer surveillance. rhTSH
(0.9 mg) was administered on days 0 and 1; values for serum
Fig. 1. Comparison of basal interleukin (IL)-6 release from human
abdominal subcutaneous and omental preadipocytes and differentiated adipocytes. Isolated preadipocytes from paired abdominal
subcutaneous or omental adipose tissue from 5 patients were either
kept in control medium (preadipocytes, P) or induced to differentiate (adipocytes, A) for 14 days. Basal IL-6 release over 4 h was
measured as described. The effect of stage of differentiation and
anatomic depot was compared by 2-way ANOVA. Results are
expressed as means ⫾ SE (n ⫽ 5).
AJP-Endocrinol Metab • VOL
290 • JUNE 2006 •
www.ajpendo.org
Downloaded from http://ajpendo.physiology.org/ by 10.220.33.1 on May 10, 2017
pausal, one of whom was treated with estrogen (transdermal) and
medroxyprogesterone. Stromal preadipocytes were isolated from each
depot, and processed in parallel, as previously described (2). Blood
vessels and fibrous tissue were carefully removed from the adipose
tissue, followed by collagenase (CLS type I; 200 U/g of tissue)
digestion. After centrifugation, size filtration, and treatment with
erythrocyte lysis buffer, equal numbers of stromal preadipocytes from
each depot for each patient were subsequently seeded (the number
varied between patients, averaging 7 ⫻ 103 cells/cm2) and grown in
DMEM supplemented with 20% FBS and antibiotics (100 U/ml
penicillin, 0.1 mg/ml streptomycin, and 50 U/ml nystatin) for a
maximum of three passages (1, 18). Stromal preadipocytes were also
sometimes cryopreserved before passaging and, once thawed, were
grown in DMEM supplemented with 10% FBS and antibiotics. This
did not alter their ability to differentiate into adipocytes (28).
For differentiation, the passaged preadipocytes from both depots
were plated at a density of 3 ⫻ 104 cells/cm2 in a 24-well plate in
DMEM supplemented with 10% FBS and antibiotics. The following
day, cells were either induced to differentiate in DMEM supplemented
with 10% FBS, 0.85 ␮mol/l insulin, 100 ␮mol/l indomethacin, 0.5
␮mol/l dexamethasone, 0.25 mmol/l isobutyl methylxanthine, and
antibiotics or maintained in control medium (DMEM with 10% FBS
and antibiotics). After the 14-day differentiation period, both stromal
preadipocytes and differentiated adipocytes from each of the two
depots were placed in DMEM supplemented with 1% calf serum and
treated with 1 ␮mol/l TSH (Sigma) or vehicle (water) for 4 h. At the
end of each experiment, medium was collected and centrifuged (500
g for 5 min at 4°C) to eliminate cell debris. The supernatant was either
kept at 4°C and analyzed in the following day or frozen at ⫺80°C
until assayed for IL-6 protein.
Measurement of IL-6 protein in conditioned medium. IL-6 protein
was measured by enzyme immunometric assay (Assay Designs, Ann
Arbor, MI), according to the manufacturer’s instructions. After the
collection of the medium, the adherent cells were lysed in Laemmli
buffer (without bromphenol blue dye; see Ref. 24), and protein
concentration was determined by modified Lowry method (Bio-Rad;
Mississauga, ON, Canada), using BSA as a standard.
Measurement of IL-6 levels in human serum. The study subjects
(approved by the Institutional Review Board of University of Pisa)
included five men aged 43 (SD 2) yr who had undergone thyroidectomy and radioablative iodine therapy for thyroid cancer. They have
been described previously (23). None had evidence of metastatic
disease and were otherwise healthy. As part of ongoing routine
follow-up care, and without discontinuation of thyroid hormone therapy, they received two separate doses of rhTSH (0.9 mg im) administered 24 h apart on days 0 and 1. Serum samples were obtained on
days 0 (before the 1st dose), 1, 2, 3, and 4 and were then frozen. IL-6
E1141
E1142
TSH STIMULATES IL-6 RELEASE FROM ADIPOSE CELLS
Fig. 2. Effect of thyroid-stimulating hormone (TSH) on IL-6
release from abdominal subcutaneous and omental preadipocytes
or differentiated adipocytes. Isolated preadipocytes from paired
abdominal subcutaneous or omental adipose tissue from 5 patients
were either kept in control medium (preadipocytes; P) or induced
to differentiate (adipocytes; A) for 14 days. Cultures were stimulated for 4 h with 1 ␮mol/l TSH or vehicle. IL-6 released in the
medium was measured as described. Results are expressed as fold
of basal release (means ⫾ SE, n ⫽ 5). Two-way ANOVA was
performed. *P ⬍ 0.05 compared with subcutaneous and omental
preadipocytes, and P ⬍ 0.01 compared with omental adipocytes.
range from undetectable to 4.6 pg/ml. IL-6 levels began to
increase by day 1, and by day 4 the mean value reached 4.7 ⫾
0.8 pg/ml. This approximately threefold response of IL-6 over
the 4 days just failed to reach significance (P ⫽ 0.05).
Samples from one of the five patients, although also showing
a clear response to TSH, started from a much higher baseline
IL-6 concentration for unknown reasons. Reanalysis of the data
without this patient results in a baseline IL-6 of 0.9 ⫾ 0.7
pg/ml, reaching a value of 4.4 ⫾ 0.9 pg/ml on day 4, an
approximately fivefold rise (P ⬍ 0.01).
To reduce the variation between all five subjects, the data
were normalized by setting the IL-6 value of the final time
point, day 4, at 100% and comparing the earlier time points as
a percentage of the respective day 4 value for each patient . The
rise in the serum IL-6 level was approximately threefold on
days 3 and 4 (P ⬍ 0.05, n ⫽ 5). Taken together, the data
indicate that rhTSH has raised serum IL-6 in these thyroidectomized patients by acting on extrathyroidal tissue(s).
DISCUSSION
Fig. 3. TSH increases serum IL-6 levels in thyroidectomized patients. Patients
received 2 injections of recombinant human TSH 24 h apart on days 0 and 1.
Serum samples were collected daily (baseline ⫽ day 0) until day 4. A: serum
TSH levels (mean ⫾ SE). B: serum IL-6 levels for each patient. C: serum IL-6
levels expressed as a percentage of day 4 responses. Repeated-measures
ANOVA was performed. *P ⬍ 0.05 compared with baseline (n ⫽ 5).
AJP-Endocrinol Metab • VOL
We previously demonstrated that mouse (3T3-L1, 3T3F442A) and human abdominal subcutaneous differentiated
adipocytes secrete IL-6 in response to TSH (5). We now report
on basal and TSH-stimulated IL-6 release in human adipose
cells at different stages of differentiation (preadipocytes and
differentiated adipocytes) and from different anatomical locations (subcutaneous abdominal and omental adipose tissue
depots).
Our data indicating that basal IL-6 release is higher from
stromal preadipocytes vs. differentiated adipocytes is consistent with several previous studies. The contribution of isolated
adipocytes to IL-6 secretion was found to be only 10% compared with that of adipose tissue fragments (14). These authors
therefore concluded that the stromal-vascular cellular fraction
in intact adipose tissue must be an important IL-6 source. A
subsequent study concurred, describing higher IL-6 secretion
from stromal preadipocytes vs. isolated adipocytes from adipose tissue obtained from lean control or leptin-deficient obese
ob/ob mice (17). Differentiation of human subcutaneous preadipocytes into adipocytes was also recently reported to markedly reduce IL-6 mRNA expression, although there was a
return to preadipocyte levels with prolonged culture time (40).
290 • JUNE 2006 •
www.ajpendo.org
Downloaded from http://ajpendo.physiology.org/ by 10.220.33.1 on May 10, 2017
TSH and IL-6 levels on days 0 – 4 are shown (Fig. 3). The
mean baseline TSH was 0.63 ⫾ 0.05 (SE) mU/l (n ⫽ 5), and
rose as expected in response to rhTSH administration. The
mean baseline IL-6 value was 1.7 ⫾ 0.9 (SE) pg/ml, with a
TSH STIMULATES IL-6 RELEASE FROM ADIPOSE CELLS
AJP-Endocrinol Metab • VOL
should be noted that the number of patients in our study was
small and somewhat heterogenous (e.g., age, sex, medical
history). With a larger and more homogeneous sample, more
subtle regulatory aspects of IL-6 release may be revealed in the
future.
To investigate the possibility of nonthyroidal action of TSH
in vivo, we used the paradigm of rhTSH administration to
patients who had been previously treated for thyroid cancer
with surgical thyroidectomy and ablative doses of radioactive
iodine. The elevation of serum IL-6 concentration in response
to rhTSH injection complements and strengthens our experiments on cultured adipose cells reported here and previously
(5). The design of the study, conducted in vivo, does not allow
precise identification of adipose tissue as the site of nonthyroidal IL-6 production. To answer that question, adipose tissue
biopsy and measurement of IL-6 expression before and after
exposure to elevated TSH levels will be required.
Others have recently used rhTSH administration in thyroidectomized patients to explore extrathyroidal action of TSH.
rhTSH treatment reduced serum vascular endothelial growth
factor levels in such patients (35). In another study, short-term
elevation of serum TSH levels did not elevate serum testosterone (23). These studies, together with our findings, suggest that
extrathyroidal action of TSH and its regulation of pro-atherogenic adipokines will require careful investigation, since substantial tissue selectivity of TSH responsiveness appears to
exist.
In summary, we show here for the first time that differentiated adipocytes derived from the abdominal subcutaneous, but
not the omental, depot are TSH responsive in terms of IL-6
release. We further report that IL-6 release in the circulation
occurs in thyroidectomized patients receiving rhTSH, indicating an extrathyroidal tissue(s) response to TSH.
ACKNOWLEDGMENTS
We thank the patients and surgeons of the Ottawa Hospital for valuable
participation.
GRANTS
This work was supported, in part, by Grant T5307 from the Heart and
Stroke Foundation of Ontario (to A. Sorisky) and National Institutes of Health
Grants EY-008976, EY-11708, and DK-063121 (to T. J. Smith).
REFERENCES
1. Adams M, Montague CT, Prins JB, Holder JC, Smith SA, Sanders L,
Digby JE, Sewter CP, Lazar MA, Chatterjee KK, and O’Rahilly S.
Activators of peroxisome proliferator-activated receptor ␥ have depotspecific effects on human preadipocyte differentiation. J Clin Invest 100:
3149 –3153, 1997.
2. Artemenko Y, Gagnon A, Aubin D, and Sorisky A. Anti-adipogenic
effect of PDGF is reversed by PKC inhibition. J Cell Physiol 204:
646 – 653, 2005.
3. Bell A, Gagnon A, Dods P, Papineau D, Tiberi M, and Sorisky A. TSH
signaling and cell survival in 3T3-L1 preadipocytes. Am J Physiol Cell
Physiol 283: C1056 –C1064, 2002.
4. Bell A, Gagnon A, Grunder L, Parikh SJ, Smith TJ, and Sorisky A.
Functional TSHR receptor in human abdominal preadipocytes and orbital
fibroblasts. Am J Physiol Cell Physiol 279: C335–C340, 2000.
5. Bell A, Gagnon A, and Sorisky A. TSH stimulates IL-6 secretion from
adipocytes in culture. Arterioscler Thromb Vasc Biol 23: E65–E66, 2003.
6. Bennet AM, Prince JA, Fei GZ, Lyrenas L, Huang Y, Wiman B,
Frostegard J, and Faire U. Interleukin-6 serum levels and genotypes
influence the risk for myocardial infarction. Atherosclerosis 171: 359 –
367, 2003.
290 • JUNE 2006 •
www.ajpendo.org
Downloaded from http://ajpendo.physiology.org/ by 10.220.33.1 on May 10, 2017
However, the literature on IL-6 production from adipose
tissue cellular fractions is somewhat controversial. In a comparison of human isolated adipocytes with adipose stromal
cells, an equivalent amount of IL-6 secretion was observed; in
addition, a vaguely defined undigested matrix component of
adipose tissue was reported to be responsible for a large part of
the IL-6 produced by adipose tissue (12). On the other hand,
immunohistochemistry analysis of human breast adipose tissue
did not detect any IL-6 reactivity in preadipocytes (29). The
reason for this is unclear, but technical limitations are a
possibility, since earlier work demonstrated IL-6 mRNA expression in stromal cells from breast adipose tissue, making it
unlikely that breast preadipocytes are unique compared with
other preadipocytes (9). Another study reported that IL-6
secretion increased during differentiation of human subcutaneous preadipocytes into adipocytes. However, the experimental
design precluded a true assessment of IL-6 secretion from
control preadipocytes, since their first measurement actually
occurred after 6 days of differentiation treatment (37).
We found that stromal preadipocytes behaved in a depotspecific fashion, with omental cells releasing more IL-6 under
basal conditions than subcutaneous cells. A parallel trend
favoring the omental depot for the differentiated adipocytes
was not significant. These responses correspond to those of
isolated adipocytes and adipose tissue fragments, which also
show this depot-related characteristic of IL-6 secretion (14).
Another study also detected the same depot-specific effect of
IL-6 secretion from adipose tissue samples; for isolated adipocytes, the trend was in the same direction, but not significant,
perhaps because of differences in collection times (12). Furthermore, we provide novel data that stromal preadipocytes
also exhibit this same depot-dependent response. The molecular basis for this depot-dependent difference in IL-6 production is not known. The previous two studies cited above used
freshly isolated adipocytes, leaving open the possibility that in
vivo influences before tissue removal might still have been
operating during the relatively brief culture period for those
cells. Because our data were derived from cells that were
maintained for 2 wk in control or differentiation medium
beyond the time for the initial cell passages, it would seem that
the depot-related difference of IL-6 release is based on inherent
attributes of the adipose cells themselves.
Adipogenesis resulted in the acquisition of IL-6 responsiveness to TSH for subcutaneous, but not omental, differentiated
adipocytes. In previous work, we did not detect any consistent
changes in TSH receptor (TSHR) protein expression upon
human adipocyte differentiation or between depots that would
account for this result; larger studies to more rigorously examine TSHR expression are warranted (4). However, we have
observed that, in the 3T3-L1 preadipocyte cell line model,
adipogenesis is associated with the ability of TSH to elevate
intracellular cAMP levels (3). Future work will need to address
whether downstream differences in TSH signaling molecules
may be operative between depots and/or during human adipogenesis as well. It should be noted that, although the release of
IL-6 by abdominal subcutaneous differentiated adipocytes is
TSH responsive, the actual amount released under these culture
conditions is smaller than that released basally by stromal
preadipocytes. Whether this will be the case for other adipokines implicated in metabolic and cardiovascular dysfunction,
such as tumor necrosis factor-␣, is an open question. Finally, it
E1143
E1144
TSH STIMULATES IL-6 RELEASE FROM ADIPOSE CELLS
AJP-Endocrinol Metab • VOL
25. Libby P. Inflammation in atherosclerosis. Nature 420: 868 – 874, 2002.
26. Menendez C, Baldelli R, Camina JP, Escudero B, Peino R, Dieguez C,
and Casanueva FF. TSH stimulates leptin secretion by a direct effect on
adipocytes. J Endocrinol 176: 7–12, 2003.
27. Mohamed-Ali V, Goodrick S, Rawesh A, Katz DR, Miles JM, Yudkin
JS, Klein S, and Coppack SW. Subcutaneous adipose tissue releases
interleukin-6, but not tumor necrosis factor a, in vivo. J Clin Endocrinol
Metab 82: 4196 – 4200, 1997.
28. Ort T, Arjona AA, MacDougall JR, Nelson PJ, Rothenberg ME, Wu
F, Eisen A, and Halvorsen YD. Recombinant human FIZZ3/resistin
stimulates lipolysis in cultured human adipocytes, mouse adipose explants, and normal mice. Endocrinology 146: 2200 –2209, 2005.
29. Path G, Bornstein SR, Gurniak M, Chrousos GP, Scherbaum WA,
and Hauner H. Human breast adipocytes express interleukin-6 (IL-6) and
its receptor system. J Clin Endocrinol Metab 86: 2281–2288, 2001.
30. Pradhan AD, Manson JE, Rossouw JE, Siscovick DS, Mouton CP,
Rifai N, Wallace RB, Jackson RD, Pettinger MB, and Ridker PM.
Inflammatory biomarkers, hormone replacement therapy, and incident
coronary heart disease: prospective analysis from the Women’s Health
Initiative obsevational therapy. JAMA 288: 980 –987, 2002.
31. Ridker PM. Clinical application of C-reactive protein for cardiovascular
disease detection and prevention. Circulation 107: 363–369, 2003.
32. Ridker PM, Rifai N, Stampfer MJ, and Hennekens CH. Plasma
concentration of interleukin-6 and the risk of future myocardial infarction
among apparently healthy men. Circulation 101: 1767–1772, 2000.
33. Rodondi N, Newman AB, Vittinghoff E, de Rekeneire N, Satterfield S,
Harris TB, and Bauer DC. Subclinical hypothyroidism and the risk of
heart failure, other cardiovascular events, and death. Arch Intern Med 165:
2460 –2466, 2005.
34. Shintani M, Nishimura H, Akamizu T, Yonemitsu S, Masuzaki H,
Ogawa Y, Hosoda K, Inoue G, Yoshimasa Y, and Nakao K. Thyrotropin decreases leptin production in rat adipocytes. Metabolism 48:
1570 –1574, 1999.
35. Sorvillo F, Mazziotti G, Carbone A, Piscopo M, Rotondi M, Cioffi M,
Musto P, Biondi B, Iorio S, Amato G, and Carella C. Recombinant
human thyrotropin reduces serum casvular endothelial growth factor levels
in patients monitored for thyroid carcinoma even in absence of thyroid
tissue. J Clin Endocrinol Metab 88: 4818 – 4822, 2003.
36. Tuzcu A, Bahceci M, Gokalp D, Tuzun Y, and Gunes K. Subclinical
hypothyroidism may be associated with elevated high-sensitive C-reactive
protein and fasting hyperinsulinemia. Endocr J 52: 89 –94, 2005.
37. Vicennati V, Vottero A, Friedman C, and Papanicolaou DA. Hormonal
regulation of interleukin-6 production in human adipocytes. Int J Obes 26:
905–911, 2002.
38. Volpato S, Guralnik JM, Ferrucci L, Balfour J, Chaves P, Fried LP,
and Harris TB. Cardiovascular disease, interleukin-6, and risk of mortality in older women: the women’s health and aging study. Circulation
103: 947–953, 2001.
39. Walsh JP, Bremmer AP, Bulsara MK, O’Leary P, Leedman PJ,
Feddema P, and Michelangeli V. Subclinical thyroid dysfunction as a
risk factor for cardiovascular disease. Arch Intern Med 165: 2467–2472,
2005.
40. Wang B, Jenkins JR, and Trayhurn P. Expression and secretion of
inflammation-related adipokines by human adipocytes differentiated in
culture: integrated response to TNF-␣. Am J Physiol Endocrinol Metab
288: E731–E740, 2005.
290 • JUNE 2006 •
www.ajpendo.org
Downloaded from http://ajpendo.physiology.org/ by 10.220.33.1 on May 10, 2017
7. Christ-Crain M, Meier C, Guglielmetti M, Huber P, Riesen W, Staub
JJ, and Muller B. Elevated C-reactive protein and homocysteine values:
cardiovascular risk factors in hypothyroidism? A cross-sectional and a
double-blind, placebo-controlled trial. Atherosclerosis 166: 379 –386,
2003.
8. Crapo LM. Subclinical hypothyroidism and cardiovascular disease. Arch
Intern Med 165: 24551–22452, 2005.
9. Crichton MB, Nichols JE, Zhao Y, Bulun SE, and Simpson ER.
Expression of transcripts of interleukin-6 and related cytokines by human
breast tumors, breast cancer cells, and adipose stromal cells. Mol Cell
Endocrinol 118: 215–220, 1996.
10. Davies TF, Ando T, Lin RY, Tomer Y, and Latif R. Thyrotropin
receptor-associated diseases: from adenomata to Graves disease. J Clin
Invest 115: 1972–1983, 2005.
11. Davies TF, Marians R, and Latif R. The TSH receptor reveals itself.
J Clin Invest 110: 161–164, 2002.
12. Fain JN, Madan AK, Hiler ML, Cheema P, and Bahouth SW. Comparison of the release of adipokines by adipose tissue, adipose tissue
matrix, and adipocytes from visceral and subcutaneous abdominal adipose
tissues of obese humans. Endocrinology 145: 2273–2282, 2004.
13. Franklyn JA, Sheppard MC, and Maisonneuve P. Thyroid dysfunction
and mortality in patients treated for hyperthyroidism. JAMA 294: 71– 80,
2005.
14. Fried SK, Bunkin DA, and Greenberg AS. Omental and subcutaneous
adipose tissues of obese subjects release interleukin-6. J Clin Endocrinol
Metab 83: 847– 850, 1998.
15. Hak AE, Pols HAP, Visser TJ, Drexhage HA, Hofman A, and Witteman JCM. Subclinical hypothyroidism is an independent risk factor for
atherosclerosis and myocardial infarction in elderly women. Ann Intern
Med 132: 270 –278, 2000.
16. Haraguchi K, Shimura H, Kawaguchi A, Ikeda M, Endo T, and
Onaya T. Effects of thyrotropin on the proliferation and differentiation of
cultured rat preadipocytes. Thyroid 9: 613– 619, 1999.
17. Harkins JM, Moustaid-Moussa N, Chung YJ, Penner KM, Pestka JJ,
North CM, and Claycombe KJ. Expression of interleukin-6 is greater in
preadipocytes than in adipocytes of 3T3-L1 cells and C57BL/6J and ob/ob
mice. J Nutr 134: 2673–2677, 2004.
18. Hutley LJ, Newell FM, Joyner JM, Suchting SJ, Herington AC,
Cameron DP, and Prins JB. Effects of rosiglitazone and linoleic acid on
human preadipocyte differentiation. Eur J Clin Invest 33: 574 –581, 2003.
19. Imaizumi M, Akahoshi M, Ichimaru S, Nakashima E, Hida A, Soda
M, Usa T, Ashizawa K, Yokoyama N, Maeda R, Nagataki S, and
Eguchi K. Risk for ischemic heart disease and all-cause mortality in
subclinical hypothyroidism. J Clin Endocrinol Metab 89: 3365–3370,
2004.
20. Janson A, Rawet H, Perbeck L, and Marcus C. Presence of thyrotropin
receptor in infant adipocytes. Pediatr Res 43: 555–558, 1998.
21. Kershaw EE and Flier JS. Adipose tissue as an endocrine organ. J Clin
Endocrinol Metab 89: 2548 –2556, 2004.
22. Kvetny J, Heldgaard PE, Bladbjerg EM, and Gram J. Subclinical
hypothyroidism is associated with a low-grade inflammation, increased
triglyceride levels and predicts cardiovascular disease in males below 50
years. Clin Endocrinol (Oxf) 61: 232–238, 2004.
23. Lado-Abeal J, Molinaro E, DeValk E, Pacini F, and Refetoff S. The
effect of short-term treatment with recombinant human thyroid-stimulating hormones on Leydig cell function in men. Thyroid 13: 649 – 652, 2003.
24. Laemmli UK. Cleavage of structural proteins during the assembly of the
head of bacteriophage T4. Nature 227: 680 – 685, 1970.